Various electronic devices use electronic switches for the user to provide inputs. For example, the electronic devices can be keyboards for computers, an input interface device for digital electronics, switch boards for complex electronic systems and/or the like. Typically, a switch is an electrical component that can be used to close or open an electrical circuit. Generally, an electromechanical switch contains two metal contacts. The two metal contacts may be brought into electrical conductance together to allow the flow of current through the switch. Therefore, the switch may be either in an ‘on’ state when the two contacts are passing current between them, or in an ‘off’ state when the two contacts are separated such that no current may transfer between the two contacts.
Such electronic devices may use arrays of electronic switches for enabling the user to provide inputs. The array may comprise rows and columns of switches. Further, the array may share a common current source and a common drain for all rows. A coordinate system may be used to designate the switches in the array. Further, digital electronics may be used to poll the electronic devices to determine the state of each switch in the array. Digital electronics allows polling for states of the switched in the coordinated system significantly faster than the human ability to switch the states of the switches. Therefore, the state of each switch in the array may not be required to be determined independently.
Similar functionality of the switches may be implemented in computer keyboards or other kinds of keypad devices. For example, U.S. Pat. No. 6,265,677 assigned to Acer Peripherals, Inc., discloses implementation of an array of switches in a computer keyboard. The keyboard uses copper printed on an integrated circuit board or a flexible material to produce the contacts. The contacts are designed in a concentric circle design with inward reaching fingers that point at the other contact but interlace such that they do not make contact. A plastic, or other material, key is placed above the contacts that when pushed down contacts the fingers to the contact and closes the electrical circuit. Therefore, a third contact such as the fingers are required to operate the switch. However, the third contact increases the complexity of design of the electrical switches.
The electronic switches used in keyboards or keypads may require a spring force to maintain separation between the contacts. For example, U.S. Pat. No. 4,580,018 assigned to Alps Electric Co., Ltd., and U.S. Pat. No. 4,490,587 assigned to Microdot Inc., disclose using spring nature of a physically deformed spring element to maintain separation. The spring element resists a compression force until a specific threshold is reached, and at that point the element may collapse and produces the contact. However, the consistency of the material of spring element is difficult to control. Moreover, the switched does not provide much electromechanical feedback. As a result, a micro-timing control of key presses is not possible. Micro timing may be essential in applications such as scientific experimentation, art, or real time interface devices. Furthermore, in most switch designs such as disclosed in U.S. Pat. No. 4,278,861 assigned to Casio Computer Co., Ltd., the actual contact of the metal contacts is generally hidden from view of the user, or is of negligible displacement. Therefore, the user may not be able to use a visual feedback to provide inputs.
A mechanism is therefore desirable to enable the user to register inputs with electronic devices.